Field of the Invention (Technical Field)
The present invention is related to the in situ production of high concentration stable aqueous biocidal solutions comprised of mixtures of free halogens, N-halosulfamic acid compounds, N-halosulfamate compounds, N,N-dihalosulfamic acid compounds and N,N-dihalosulfamate compounds, with or without additional biocidally active components, in any desired compositional mixture and at a desired pH through an electrolysis process, where the nature of the biocidal solution is determined by the nature of the brine used in the electrolysis process as well as the operational parameters of the electrolytic process.
Background Art
Note that the following discussion may refer to a number of publications and references. Discussion of such publications herein is given for more complete background of the scientific principles and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
Aqueous free halogen species such as chlorine, bromine, iodine, hypochlorous acid, hypobromous acid, hypoiodous acid, hypochlorite, hypobromite, and hypoiodite are known to be very powerful anti-microbial agents and are often used in water disinfection applications. Along with a high level of biocidal activity, aqueous free halogens are also highly chemically reactive to other species often present in waters undergoing treatment. These species include natural organic matter, synthetic and natural organic chemicals, iron, manganese, hydrogen sulfide, ammonia, arsenic, and other chemicals. The presence of these free halogen demanding substances consume free halogens added to the water that would otherwise be useful in inactivating microorganisms, thus, this process could be considered detrimental to the overall treatment process if the free halogen consuming chemical reaction is not desirable. Reactions between aqueous free halogens and organic material present in the water being treated can also, in some cases, lead to the undesirable products such as the formation of halogenated organic chemicals such as trihalomethanes and haloacetic acids. Therefore, the treatment of waters containing high amounts of these halogen-reactive compounds is often advantageously accomplished through the use of biocides that are less chemically reactive than aqueous free halogen species.
Haloamines, which can broadly be considered as chemical species which contain at least one nitrogen-halogen bond, are often used in place of oxidizing free halogens to provide a disinfectant for water treatment. While haloamines are effective biocidal compounds, they are also much less chemically reactive as compared to free halogens. Thus, in waters containing substantial amounts of free halogen demanding substances, haloamines have the potential to provide a substantial benefit to the overall water disinfection process. Aqueous solutions of haloamines are typically produced through a chemical reaction between an aqueous free halogen species and a compound containing at least one nitrogen-hydrogen bond whereby the chemical reaction produces a compound containing at least one nitrogen-halogen bond. Ammonia or ammonium ions are the most common source of the nitrogen containing compound used in this process, although other nitrogen containing compounds are often utilized as well.
One major deterrent to the use of haloamines, and especially haloamines produced through the reaction of ammonia or ammonium ions with an aqueous free halogen species, is that they are highly unstable, especially at higher concentrations (i.e. greater than 10 mg/L); see for example Audrieth, L. F.; Rowe, R. A. “The Stability of Aqueous Chloramine Solutions” J. Am. Chem. Soc. 1955, 77, 4726-4728. Due to the instability of haloamines, it is typically not possible to produce concentrated haloamine solutions and ship them to a point of application. As a result, haloamines derived from ammonia or ammonium ions are often produced in situ during treatment by the action of aqueous free halogens on ammonia or organic amines naturally present or added to water being treated. Alternatively, it is sometimes desirable to prepare concentrated aqueous haloamine solutions derived from the reaction between ammonia or ammonium ions at the point of application and then use these formed haloamine solutions as a primary disinfectant. Situations where this could be advantageous include the treatment of waters which have a known or highly variable free halogen demand which would consume free halogens without the benefit of microbial inactivation but which can be effectively treated with a haloamine disinfectant.
Sulfamic acid and its organic compound derivatives, known as sulfonamides (for example, toluenesulfonamide), are chemically distinct from ammonia or other organic amine-containing compounds used to produce haloamines but, like ammonia or many amines, typically contain a nitrogen-hydrogend bond which can react with aqueous halogen species. Products of the reaction between sulfamic acid, having the chemical formula H3NSO3, and an aqueous halogen species are N-halosulfamate compounds (either N-halosulfamate, having the chemical formula HNSO3X−, or N-halosulfamic acid, having the chemical formula H2NSO3X), N,N-dihalosulfamate compounds (N,N-dihalosulfamic acid, having the chemical formula HNSO3X2, or N,N-dihalosulfamate, having the chemical formula NSO3X2−), or combinations thereof, where, in all cases, the letter X represents a halogen (i.e. Cl, Br, I). Products of the reaction between and organic sulfonamide compounds, having the chemical formula of RSO2NH2, and an aqueous halogen species are N-halosulfanomide compounds, having the chemical formula of RSO2NHX, N,N-dihalosulfonamide compounds, having the chemical formula of RSO2NX2, or combinations thereof, where, in all cases, the letter R represents and organic functional group comprising at least carbon and hydrogen and the letter X represents a halogen (i.e. Cl, Br, I). These compounds can stabilize the electrolyzed halogen species.
U.S. Pat. No. 3,776,825 to Vit entitled “Electrolytic Treatment” discloses that a brine comprising a halide ion source and an amine compound both dissolved in water is first pH adjusted through the addition of a base such as sodium hydroxide, and then electrolyzed, thereby producing a solution containing one or more haloamine compound, including N-chlorosulfamates or N-chlorosulfonamides produced from sulfamic acid or organic sulfonamides, respectively. Vit further teaches that when electrolysis is used to make these haloamine solutions they are unstable, and therefore the invention descried by Vit is focused entirely on the instantaneous production and immediate subsequent use of the produced haloamines as opposed to the production of stable haloamine solutions. Because Vit discloses the addition of NaOH to the brine prior to electrolysis, and discloses that the pH of the solution is thus greater than 12, the solution prior to electrolysis no longer comprises sulfamic acid, but instead comprises sulfamate ions.